DETECTION OF CORONARY VASOSPASM BY POSTHYPERVENTILATION TC-99M SESTAMIBI SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY IMAGINE IN PATIENTS WITH CORONARY-ARTERY DISEASE

Forced hyperventilation is simple, safe to perform, and can be used as a provocative test for coronary vasospasm. This study assesses whethe r a vasospastic component of angina might be detected in patients with angiographically ''nonobstructive'' coronary artery disease by posthy perventilation technetium-99m (Tc-99m) sestamibi single-photon emissio n computed tomography (SPECT) cardiac imaging, Eleven patients with an giographically nonobstructive coronary artery disease underwent Tc-99m sestamibi SPECT imaging at rest and after forced hyperventilation. Ve ssel diameters were measured by quantitative angiography before and af ter forced hyperventilation, and posthyperventilation SPECT images wer e compared with dipyridamole Tc-99m sestamibi stress images, Forced hy perventilation resulted in a 15% reduction in coronary artery diameter in stenotic segments (p < 0.01), and a 17% reduction in adjacent nons tenotic segments (p < 0.001). Myocardial uptake of Tc-99m sestamibi in segments perfused by vessels with angiographically nonobstructive ste noses was reduced 24% following forced hyperventilation (p < 0.001) co mpared with only 4% following dipyridamole (p < 0.02), These findings suggest that posthyperventilation Tc-99m sestamibi SPECT imaging in pa tients with angina pectoris and nonobstructive coronary artery disease may be useful in identifying a vasospastic component of angina. (C) 1 998 by Excerpta Medico, Inc.